objective-c - 设置 UITextField inputAccessoryView 的 alpha 不起作用

Question

显示inputAccessoryView成功，但它完全是黑色的。

    _textField = [[UITextField alloc] initWithFrame: CGRectZero]; // update frame later
    _textField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;

    UIView *inputAccessoryView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 180)];
    inputAccessoryView.backgroundColor = [UIColor blackColor];
    inputAccessoryView.alpha = 0.2;

    _textField.inputAccessoryView = inputAccessoryView;

我对此感到完全困惑......谁能解释它为什么会发生？

Answer 1

在上一行使用这种 UIColor 方法而不是设置 alpha：-

[UIColor  colorWithHue:saturation:brightness:alpha:];